An optical computer mouse uses a light source and image sensor to detect mouse movement relative to an underlying tracking surface to allow a user to manipulate a location of a virtual pointer on a computing device display. Two general types of optical mouse architectures are in use today: oblique architectures and specular architectures. Each of these architectures utilizes a light source to direct light onto an underlying tracking surface and an image sensor to acquire an image of the tracking surface. Movement is tracked by acquiring a series of images of the surface and tracking changes in the location(s) of one or more surface features identified in the images via a controller.
Optical mice may be configured to detect an “off-surface condition” when the mouse is lifted off of a tracking surface. The detection of an off-surface condition allows the operation of the mouse to be adjusted in response to being lifted off of the tracking surface. For example, the light source of the mouse may be dimmed or shut off when the mouse is lifted off of the tracking surface to preserve battery life. Furthermore, the tracking of motion also may be suspended until the mouse is again placed on the surface. However, ambient light may affect off-surface detection, and therefore may affect mouse performance.